/* DH_HASH.C
 * Copyright (c) 2007 MissingNODE 
 * Based on GPL OpenQM Code
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2, or (at your option)
 * any later version.
 * 
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software Foundation,
 * Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 * 
 * 
 * START-HISTORY:
 * Oct-10-2007 Initial Revision
 * END-HISTORY
 *
 * START-DESCRIPTION:
 *
 * END-DESCRIPTION
 *
 * START-CODE
 */

#include <tm.h>
#include <dh_int.h>

#define HASH_MAGIC 0x5646A2C3

private unsigned char bits[] = {
0x00, 0x80, 0x40, 0xC0, 0x20, 0xA0, 0x60, 0xE0, 
0x10, 0x90, 0x50, 0xD0, 0x30, 0xB0, 0x70, 0xF0, 
0x08, 0x88, 0x48, 0xC8, 0x28, 0xA8, 0x68, 0xE8, 
0x18, 0x98, 0x58, 0xD8, 0x38, 0xB8, 0x78, 0xF8, 
0x04, 0x84, 0x44, 0xC4, 0x24, 0xA4, 0x64, 0xE4, 
0x14, 0x94, 0x54, 0xD4, 0x34, 0xB4, 0x74, 0xF4, 
0x0C, 0x8C, 0x4C, 0xCC, 0x2C, 0xAC, 0x6C, 0xEC, 
0x1C, 0x9C, 0x5C, 0xDC, 0x3C, 0xBC, 0x7C, 0xFC, 
0x02, 0x82, 0x42, 0xC2, 0x22, 0xA2, 0x62, 0xE2, 
0x12, 0x92, 0x52, 0xD2, 0x32, 0xB2, 0x72, 0xF2, 
0x0A, 0x8A, 0x4A, 0xCA, 0x2A, 0xAA, 0x6A, 0xEA, 
0x1A, 0x9A, 0x5A, 0xDA, 0x3A, 0xBA, 0x7A, 0xFA, 
0x06, 0x86, 0x46, 0xC6, 0x26, 0xA6, 0x66, 0xE6, 
0x16, 0x96, 0x56, 0xD6, 0x36, 0xB6, 0x76, 0xF6, 
0x0E, 0x8E, 0x4E, 0xCE, 0x2E, 0xAE, 0x6E, 0xEE, 
0x1E, 0x9E, 0x5E, 0xDE, 0x3E, 0xBE, 0x7E, 0xFE, 
0x01, 0x81, 0x41, 0xC1, 0x21, 0xA1, 0x61, 0xE1, 
0x11, 0x91, 0x51, 0xD1, 0x31, 0xB1, 0x71, 0xF1, 
0x09, 0x89, 0x49, 0xC9, 0x29, 0xA9, 0x69, 0xE9, 
0x19, 0x99, 0x59, 0xD9, 0x39, 0xB9, 0x79, 0xF9, 
0x05, 0x85, 0x45, 0xC5, 0x25, 0xA5, 0x65, 0xE5, 
0x15, 0x95, 0x55, 0xD5, 0x35, 0xB5, 0x75, 0xF5, 
0x0D, 0x8D, 0x4D, 0xCD, 0x2D, 0xAD, 0x6D, 0xED, 
0x1D, 0x9D, 0x5D, 0xDD, 0x3D, 0xBD, 0x7D, 0xFD, 
0x03, 0x83, 0x43, 0xC3, 0x23, 0xA3, 0x63, 0xE3, 
0x13, 0x93, 0x53, 0xD3, 0x33, 0xB3, 0x73, 0xF3, 
0x0B, 0x8B, 0x4B, 0xCB, 0x2B, 0xAB, 0x6B, 0xEB, 
0x1B, 0x9B, 0x5B, 0xDB, 0x3B, 0xBB, 0x7B, 0xFB, 
0x07, 0x87, 0x47, 0xC7, 0x27, 0xA7, 0x67, 0xE7, 
0x17, 0x97, 0x57, 0xD7, 0x37, 0xB7, 0x77, 0xF7, 
0x0F, 0x8F, 0x4F, 0xCF, 0x2F, 0xAF, 0x6F, 0xEF, 
0x1F, 0x9F, 0x5F, 0xDF, 0x3F, 0xBF, 0x7F, 0xFF};

#define RotateRight5(n) (unsigned long int) ((((unsigned long int)(n) >> 5) | ((unsigned long int)(n) << 27)))

/* ====================================================================== */

long int hash(id, id_len)
   char id[];
   short int id_len;
{
 char * p;
 long int hash_value = 0;
 union
  {
   long int val;
   unsigned char chr[4];
  } in, out;


 for (p = id; id_len--; p++)
  {
   hash_value ^= *p;
   hash_value = RotateRight5(hash_value);
  }
 
 in.val = hash_value * HASH_MAGIC;
 out.chr[0] = bits[in.chr[3]];
 out.chr[1] = bits[in.chr[2]];
 out.chr[2] = bits[in.chr[1]];
 out.chr[3] = bits[in.chr[0]];

 return out.val & 0x7FFFFFFFL;
}


/* ====================================================================== */

long int dh_hash_group(fptr, id, id_len)
   FILE_ENTRY * fptr;
   char id[];
   short int id_len;
{
 long int hash_value;
 long int group;
 char u_id[MAX_ID_LEN];

 if (fptr->flags & DHF_NOCASE)
  {
   memucpy(u_id, id, id_len);
   hash_value = hash(u_id, id_len);
  }
 else
  {
   hash_value = hash(id, id_len);
  }

 group = (hash_value % fptr->params.mod_value) + 1;

 if (group > fptr->params.modulus) 
  {
   group = (hash_value % (fptr->params.mod_value >> 1)) + 1;
  }

 return group;
}

/* END-CODE */
